Typically, work vehicles, such as tractors and other agricultural vehicles, have a continuously variable transmission (CVT) or a power shift transmission (PST). Conventionally, each type of transmission utilizes a parking brake in order to maintain the vehicle in a parked or stopped condition when the vehicle is placed in park or when performing a hill holding operation. In addition, the parking brake may also be used to reduce the speed of the work vehicle, such as when the work vehicle experiences a loss of functionality (e.g., loss of electrical power and/or hydraulic pressure) that requires the vehicle to be stopped immediately.
In many instances, conventional parking brakes for work vehicle transmissions are configured to be engaged and disengaged via an electric actuator (e.g., a solenoid activated actuator). In particular, the electric actuator is typically configured to apply a linear force through a cable extending between the actuator and a corresponding lever arm, which is, in turn, rotatably coupled to the parking brake. By providing a tensioning force on the cable, the electric actuator causes the lever arm to rotate, thereby engaging the parking brake. Similarly, by releasing the tensioning force on the cable, a spring coupled directly to the lever arm may cause the lever arm to rotate in the opposite direction, thereby disengaged the parking brake.
Unfortunately, several disadvantages are typically associated with the use of electric actuators for engaging and disengaging parking brakes. Specifically, the electric actuators typically present mounting challenges within the work vehicle, since the actuator is often mounted at a location that is significantly spaced apart from the transmission. In addition, operation of an electric actuator requires the use of complex computer logic to ensure that the associated parking brake is engaged and disengaged at the appropriate time. However, even despite the use of complex computer logic, system faults (e.g., short circuits, etc.) may often result in the electric actuator being unintentionally commanded to engage the parking brake, which can cause significant damage to the brake itself or to the transmission as a whole when the vehicle is still in motion.
Accordingly, an improved parking brake system that provides an alternative to the use of electric actuators would be welcomed in the technology.